Electron multiplier devices are used in many applications to multiply incidental charges through secondary emission. Electron multiplier devices can take a single electron, and via secondary emission, can induce emission of more electrons from an emissive material. This process can be repeated to multiply a single detected electron (e.g., an electron passing through the electron multiplier device) into a larger number of electrons that are directed towards a metal anode for detection. Certain electron multiplier devices, such as channel electron multipliers and channeltrons (“CEM”), offer a high dynamic range of electron multiplication to assure an absolutely linear response, which results in electron multiplier devices having capabilities beyond the limits of most analytical instruments. Due to their low mass and high gain, electron multipliers are used in many nuclear physics labs and space applications to count electrons and charged particles (e.g., in a pulse mode of operation). Electron multipliers may be used in mass spectrometry applications, residual gas analyzers, plasma analysis applications, Auger electron spectroscopy applications, electron spectrometers, secondary electron multiplier devices, focused ion beam emitters, and leak detectors.
In general, CEMs are made out of single tube and can be referred to as one dimensional devices. In contrast to CEMs, another geometry of continuous-dynode electron multiplier is called the microchannel plate (“MCP”), which is two-dimensional arrays of microscopic channel electron multipliers. MCP photo-multipliers (“MCP-PMT”) are an evolution from the basic principles of photo-multipliers. MCP-PMTs utilize planes of small pores, which form the amplification sections of the complete MCP-PMT devices. Current MCP-based detectors have shown unique properties such as high gain, high spatial resolution, high timing resolution, and very low background rate. These properties make MCP detectors useful in a wide variety of applications including low-level signal detection, photodetection, gas electron multipliers (“GEM”), time-of-flight (“ToF”), mass spectrometry, molecular and atomic collision studies, electron microscopy, field emission displays, night vision goggles and binoculars, and high speed and resolution cameras. At present, small area conventionally made MCPs are extensively used in photo-detection for visible light night vision applications and used in photodetectors for high energy physics and nuclear physics.
Conventional MCPs are fabricated using multi-fiber glass working techniques to draw, assemble, and etch an array of solid core fibers resulting in channels in a thin wafer of lead silicate glass. Although pore diameters as small as six microns have been achieved, these channels are typically ten to forty microns in diameter, have an aspect ratio (α=(L/D)=pore length/pore diameter) of sixty to one hundred, and have an open area ratio (i.e., fraction of surface covered by pores) of fifty to seventy-five percent. Thermochemical processing (e.g., H2 firing) is used to activate the channel walls for electron multiplication, and metal electrodes are evaporated onto both faces to provide electrical contact. More recently, techniques have been developed for creating capillary glass arrays and subsequently coating the arrays with thin, conformal films that provide electrical conductivity and secondary electron emission properties. Exemplary MCPs manufactured using capillary glass arrays are described in U.S. Pat. No. 8,969,823, entitled “MICROCHANNEL PLATE DETECTOR AND METHODS FOR THEIR FABRICATION,” dated Mar. 3, 2015, which is herein incorporated by reference in its entirety and for all purposes.
However, current MCPs are limited in performance and are expensive to manufacture. The etching required for solid core, lead glass MCPs add to the manufacturing costs and limits the electron gain of the given MCP. Moreover, the hydrogen firing dictates both the MCP resistance and the secondary emission, and so these properties cannot be independently varied. Finally the lead glass utilized is brittle and hygroscopic, which causes MCPs to be prone to breakage during handling. The capillary glass method overcomes some of these limitations; however, fabricating the capillary glass arrays is very labor intensive. For example, the capillary glass method requires manual alignment of thousands of hollow glass tubes, which translates to high manufacturing costs.